This invention relates to covered railway hopper cars designed to withstand internal pressure.
In U.S. Pat. No. 3,269,779 a stub sill railway hopper car designed to withstand up to 15 psi includes an arcuate top portion struck from a constant radius. Longitudinally extending upper chords are located at the juncture of the top portion with side sheets extending inwardly and downwardly from the upper chords on opposite sides of the car. Longitudinally extending side sills are located on the lower portion of the side sheets on each side of the car. Boxed channel reinforcing members are located adjacent vertical bulkheads inside the car which extend throughout the arcuate top portion and down the side sheets. Transverse reinforcements also extend between the longitudinal upper chords above each hopper outlet. Formation of the arcuate roof is difficult and expensive. Furthermore the box channel reinforcements add considerable weight to the car.
In U.S. Pat. No. 3,339,499 a stub sill covered hopper car is disclosed in which a curved roof extends between top chords located on opposite sides of the car. Curved side sheets extend downwardly to side sills extending longitudinally of the car. In adapting this car to withstand moderate internal pressure of around 5 psi, the top chords are reinforced by a rib stiffener extending one-two (1-2) feet down the side sheet and welded to the side sheet. See for example, ACF Shippers Car Line Brochure No. SCL-CF42 December 1969, copy in application file.
When pressure is applied to the interior of a covered hopper car such as that illustrated in U.S. Pat. No. 3,339,499, the top chord as shown in FIGS. 1 and 2, is loaded in the following manner. The membrane force Pr.sub.2, internal pressure acting in a direction perpendicular to the roof times the radius of curvature in roof sheet 10, loads roof 10 with a uniform continuous load. The membrane force Pr.sub.1, acting in a direction perpendicular to the side sheet 14, loads side sheet 14 with a uniform continuous load. The eccentricity of loads Pr.sub.2 and Pr.sub.1 with respect to the centroid of the top cord causes a moment M in the Z direction (FIG. 2).